TS820-based Analog Wall Dimmer for LED Lamps

Created: Apr 11, 2017

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Description

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Summary

Silicon-Controlled Rectifier (SCR) dimmers are designed to be used for resistive loads such as halogen and incandescent lamps. However, SCR dimmers are not compatible with LEDs since LEDs are not resistive loads. Because of this, the LED may not dim as expected since LEDs are either on or off, so light levels may not change as users anticipate or the light may flicker and this flicker may shorten an LED’s usable life. This reference circuit is designed to provide solution to the flickering phenomenon of LEDs. This is done by applying a continuous current through the gate.

This reference design is comprised mainly of SCRs, LC filters, gate resistors, and turn-on delay capacitors. This circuit operates at an RMS voltage of 98 - 132V. Also, it is important mount 27 °C/W heatsinks with the SCRs. In this design, the two TS820-600FP SCRs are connected in reverse parallel. The 220kΩ potentiometer is used to adjust the delay of the SCR in which in this design is set to 0.7ms at maximum power and 8.4ms at minimum power. It is also necessary to use a 5A fuse to protect the SCR in case of lamp flash-over or accidental short-circuit. A 29uH inductor and a 100nF capacitor are used as LC noise filter.

This reference circuit is specifically designed as dimmer for LED lamps. This low-cost analog dimmer topology using a sensitive SCR TS820-600FP can drive typical low-consumption lamps, particularly CFL and LED dimmable lamps.